For certain spine injuries, the use of an implantable spinal fixation device is indicated to join two or more vertebrae together. A common form of spinal fixation includes utilizing an elongate spinal rod oriented generally parallel to the spine and spaced laterally to one side of the spine. This rod is coupled to at least two vertebrae, and often more than two vertebrae, through various different fixation fasteners. One common form of fixation fastener is a pedicle screw which is screwed directly into the pedicle of each vertebrae. These pedicle screws have portions thereof which can be secured to the rod.
Typically, two spinal rods are provided on opposite sides of the spine with at least two pedicle screws on each rod. The resulting arrangement secures the two vertebrae together while maintaining spacing between the vertebrae and transferring vertical loads along the spinal rod, rather than directly between the vertebrae, so that damaged vertebrae can still function by passing vertical loads through this spinal fixation device.
Often it is beneficial for these two spine rods to be coupled together to prevent relative motion therebetween, or to at least limit such relative motion. Crosslinks are known in the prior art which act as mechanical couplings to secure the two spine rods together. Such crosslinks generally include fasteners which allow them to be fastened to the rod on each end of the crosslink. Because the orientation of the two rods relative to each other as well as the distance between the rods can vary significantly, various different crosslinks have been designed which include adjustability features so that the crosslinks can secure the two rods together in a variety of different configurations and still provide a rigid link between the two spine rods once the crosslink has been fixed in place.
Such adjustable crosslinks known in the prior art are exemplified by crosslinks and related structures disclosed in U.S. Pat. Nos. 5,330,473, 5,601,554, 5,667,507, 5,676,665, 5,707,372, 5,709,684, 5,752,955, 5,947,965, 6,139,548, 6,238,396, 6,485,491, 6,524,310, 7,104,993 and 7,122,036 and U.S. Published Patent Application Nos. 2003/0004512, 2003/0114853, 2005/0090821, 2005/0228377, 2006/0064093, 2006/0241598, 2006/0271045 and 2006/0271051. These prior art crosslinks have been less than entirely adequate in that they either do not provide a high degree of adjustability to easily fit all potential different spine rod relative orientations, or they are not easily adjusted or used by the surgeons in the surgical setting.
In some instances a surgeon will even choose not to utilize any crosslink because known crosslinks have been too difficult to fix in place or provide insufficient additional stability to the overall spinal fixation implant to warrant the difficulty associated with their implantation. Furthermore, the spine itself can interfere with the crosslink by blocking a straight path between the two rods, making many such prior art crosslinks unable to fit as desired. Accordingly, a need exists for a crosslink which can join two spine rods of a spinal fixation system together which is easy for the surgeon to use and which is highly adjustable to provide the most preferred interconnection between the two spine rods.